Integrating gradiometer



Sept. 23, 1947. E. M. MeNA-r-r s Re. 22,919

' INTEGRATIE@ GRADIouEm l Original Filed Aug. 8, 1941 2 Sheets-Shoot 1 l 2e 32 25\ .f ../27

Sept. 23, 1947. E. M. McNATr Re. 22,919

I IMEGMTING GRDIOIETBR origina; Filed Aug. e; 1941 2 sheets-sheet 2 Reissued Sept. 23, 1947 v Re. V gz-,919

INTEGRATIN G GRADIOMETER Eugene M. McNatt, Tulsa, Okla., assignor to Standard Oil Develo ration of Delaware pinent Company, a corpo- ()riginal No. 2,320,290,'dated May 25, 1943, Serial No. 405,910, August 8, 1941. reissue May 24, 1944, Serial No.

10 Claims. (Cl. 33-v141.5)

elevation survey adds considerably to the expenseV of the prospecting method and, in addition, is time consuming.

It is the principal object of the present invention to provide a meth'od and apparatus for making elevation surveys while traveling in a vehicle over an area tobe surveyed. An

additional object of the present invention is the' provision of an apparatus of the character described, which will be substantially` unaiectedy by changesin speed of the vehicle or undulations of the terrain.

A further object of the present invention is the provision of a device of the character described, in whichmeans are provided for subjecting a photocell to flashes of light of a numberproportional to the distance covered by the vehicle and to the sine of the angle which the longitudinal axis of the vehicle makes with the horizontal.

Further objects and advantages of the present invention will appear in the following detailed description of the accompanying drawings, in whichf Figure 1 is a side elevation partly in section of one type of apparatus according to the present invention;

Figure 2 is a sideelevation, partly in section,

of the shutter, which forms part of the combination shown in Figure 1;

Figure 3 isa front elevation of the pendulum system;

Figure 4 is a diagrammatic view of the accel- I designates a nat base which may rest on the floor of `the vehicle, but which is preferably carried by arms'3l at its either end, said arms vnaled a sh'aft ,3.

Aof magnets 5,

ApplicationY for 537,167 I uprights 33. To avoid friction the bar is journaled in ball bearings. On one end of the base is a pair of spaced uprights 2 on which is jour- The shaft carries a. p'air of spaced aluminum discs 4. Around the periphery of each of these discs is arranged a plurality suitably supported by the uprights 2. Thus, the periphery of the disc cuts through a plurality of magnetic fields, whereby when the disc rotates eddy currents are set up in` it, which, in conjunction with th'e magnetic elds, damp the movementof the disc. The shaft 3, (See Fig. 6) is broken intermediate its ends. It carries a pair of spaced plates 6, to which is bolted an armature l. Wound axially on the armature is a coil 8. In spaced relation to the armature is a permanent magnet 9, which may besuitably supported by legs Il), fixed to the base I. Suspended from the armature is a pendulum I`I.

Fixed to the shaft 3 in such a manner as to have its axis of rotation coincident with th'e axis of the shaft is a mirror I2.

Spaced from the uprights 2 `a selected distance, there is fixed to the base I a post Il. Near its bottom, this post carries a collar I 4, which forms a bearing track for a worm gear I5. Fixed to the upper face of this gear is a shutter I6. This shutter may have any desired configuration, meeting thev requirements hereinafter specified. In the embodiment shown the shutter, if laid iiat, would resemble 'two saw teeth. The worm gear is driven by a worm 34 which is connected through gearing in the gear box I1 to'a, flexible shaft I8, geared to the drive shaft of the vehicle. gearing in the gear box is a flexible sh'ait I9, which is. supportedI by the base I by ,suitable brackets, and which carries at its end a toothed disc 2D. Mounted behind the disc 20 is a light source 2|, arranged so as to cast a beam of light on mirror; I2 through-the notches on the periphery of disc 20. The ligh't source is the pin hole type. Arranged 'in the path of travel of the light from source- 2| to mirror I2 is a lens 22, so selected as to focus the beam of light on the surface of the Ishutter I6.

Fixed to the posty I3 is an ellipticalmirror 23, which, in this embodiment, constitutes part of an ellipse of which th'e axis of shaft 3 is one of the focal points. ellipse, of which mirror 23 is a part, at the other focal point of said ellipse, is a photocell 24. With this arrangement of.. parts light l reflected from mirror I2 to the mirror 23 will in turn be depending from a. bar 32 pivtally mounted in 55 reflected onto the photocell 24; vThe output of Also driven'by a suitable Arranged on the axis of the ployed. It

' angle 6 with the 3 y the photocell is delivered to an ampliiier 25 which in turn feeds a scaling circuit contained in unit I out two pulses per second. The output of the ircuit is delivered toa counter .21 of rlcal impulse type.

scaling the elec As will appear from the operation of the apparatus shown is based on the delivery` to the counter of a number of pulses which will depend upon the distance travelied by the vehicleJ and on the sine of the angle which the longitudinal axis of the vehicle -makes with the horizontal. There are, accordingly, certain requirements for the type of shutter emmust be one which, for a given deviation of the vehicle fromithe horizontal. will transmit a number of light flashes proportional to In one has been found that 1500 ashes of light per `revolution of the shutter is satisfactory.

In order to avoid any errors which might be incurred by reason of movement being imparted to the pendulum by sudden acceleration or de`- celeration of the vehicle, the compensator, composed of armatures 1 and coil 8 previously referred to, is provided. Coil 8 is connected to an ac- -celerometer 28, whichas shown in Figure 4, consists of a D. C. generator 2e, which generates the foregoing description,

the sine of the angle which the vehicle makes y with the horizontal. i

To illustrate, the arrangement shown in Figure lis in horizontal position, in which the beam of iight from the mirror I2 strikes the shutter at point A, which may be considered the null point.

If the vehicle encounters a rise, the point of incide-nce of the light beam on the shutter will be below A, while if the vehicle encounters a drop, the point of incidence will be above A. If it be assumed that the vehicle'encounters a drop which causes its longitudinal axis to make an horizontal, the light beam from mirror yI2 will deviate from the horizontal by angle equal to 20. It will be understood, of course, that the mirror itself, in this case., will deviate from the null position by an angle equal to 6, but this angle will be doubled in the reflected beam. The point at which the beam of light will then strike the surface of the shutter i6, will be above the horizontal a distance equal to y. At this elevation of the shutter, the open space must be of a width equal to a+k sin o, where a equals the Width of the shutter opening at the `height on the shutter corresponding to the null point A, and k is a. constant, depending upon the distance between the mirror and the shutter, and the dimensions of the shutter. It is to be emphasized that where the width of the shutter is referred to, reference is Vmade to the circumferential distance between edges of the shutter. In effect, therefore, a. actually represents' that fraction of the period of revolution of the shutter during which the light beam passes through the shutter when the vehicle is inthe horizontal position. Likewise, for any value of y, the shutter must be open for a period corresponding to a-i-k sin 0. r

Thus, the shutter contributes to the overall result the desired relationship between the period for which the light cell is exposed to light and the inclination of the vehicle to the horizontal. The number of pulses recorded, however, also must be proportional to the distance travelled by the vehicle. the result by the notched disc 20, which, as previously stated, revolves at a speed bearing a fixed ratio to the speed of travel of the vehicle. It may be noted that the greater the number of notches on the periphery of the disc 2D, the more accurate will be the results for a given ratio of disc speed to vehicle speed. The accuracy can also be increased by increasing this latter ratio.

This relationship isbrought into voltage proportional to its speed of rotation. This generator is geared directly to the drive shaft of the vehicle, and accordingly generates voltage proportional to the speed of the drive shaft. One output terminal of the generatoris connected to the coil 8, and the other output terminal is connected to one plate of the condenser 30, the other plate of which is connected to the coil 8. If the speed of the drive shaft remains constant, no current passes through the condenser. Any change of speed of the drive shaft will give rise to a change in value of the voltage output of the generator and this change in voltage will cause a current to flow through the condenser, and thus through c0118. Since coil 8 is in a magnetic field, any current flowing Athrough coil 8 .will give rise to a torque opposing the movement of the armature on which the coil is mounted, provided it is properly wound on the armature for this purpose. Since the pendulum is rigidly fixed to the armature, the current in coil 8 will have the effect of curbing the tendency of the pendulum to oscillate upon acceleration or deceleration of the vehicle;

It is to be understood that the particular `embodiment described above is simply one embodiment of the present invention. Many variations in the arrangement of the elements and the particuiar elements themselves are possible without departing from the principle of operation. For example, the shutter may assume many shapes, which will satisfy the relationship that for a given value of y the opening time of the shutter must have a value corresponding to a-Hc sin 0. A

In fact, the shutter can be so constructed that a is 0, and, therefore; need not be brought into the calculations. This would, of course, necessitate two separate photocells and associated counters, one for positive values of 0, and one for negative valuesof H.

In the use of the device, the valuesrecorded by the operator are the distance traveled and thev number of counts on the counter. With this data,'the. change in elevation 'can be calculated from the equation bAH-:AN-CAL in which AH is the difference in elevation between two points in question,

AN is the number of the two points,

AL is the odometer reading between the two points in question, and

c and b are calibration constants depending counts recorded between upon the dimensions of the apparatus. c may between two points having a known elevation' difference. y

The nature and objects of the present invenembodiment oi' the presentpinvention it the l tion having been thus described and illustrated, what is claimed as new and useful and is desired to be secul ed by Letters Patent is:

l. In a method for determining variations in elevation of terrain traversed by. a vehic1e the steps which comprise creating a repeating signal of a frequency proportional to the rate of travel of the vehicle', transmitting to an indicating device a number of repetitions of said signal proportional to the sine of the angle which the longitudlnal axis of said vehicle makes with the horizontal, and exposing for observation the repetitions of the signal so transmitted.y

2. In a method for determining the changes in elevation of terrain traversed by a vehic1e the steps which comprise producing periodic light flashes of a frequency which varies with the speed of travel of the vehicle, transmitting to a light sensitive indicator a number of said flashes proportional to the sine of the angle which the longitudinal axis of the vehicle makes with the horizontal, and exposing for observation a value which is a, function of the number of light flashes reaching said indicator.

3. An apparatus for determining the variations in elevation of terrain traversed by a vehicle comprising means mounted in said vehicle for creating a signal, means for controlling the frequency of said signal as a function of the speed of travel of said vehic1e, means for transmitting' said sig.. nal to an indicator, means interposed between the point of creation of said signal and the indicator for fixing the number of signals reaching the indicator at a value proportional to the sine of the angle which the longitudinal axis of the vehic1e makes with the horizontal, and means for exposin for observation a value proportional to the num er of signals which reach the indicator.

4. An apparatus for determining variations in elevation of terrain traversed by a vehicle comprising a lightv source in said vehicle, means for creating flashes of light from said source of a frequency proportional to the speed of travel of said vehicle, light sensitive indicatingmeans arranged to receive said light flashes, and means interposed between said light source and said steps which comprise creating a repeating sigindicating means for blocking oir a. predeterl mined number of said light dashes fixed so that the number of light dashes reaching said indicating means is a function of the sine of the angle which the longitudinal axis of the vehicle mounted on said base perpendicularly to the.-

longitudinal axis of said vehic1e, a pendulum carried by said shaft. a. mirror mounted on said shaft. a light source arranged to direct its beam on said mirror. means interposed between said 6 llight source and said mirror for cutting off said light beam with a periodicity depending upon the speed of travel of said vehicle to thereby produce light flashes, a second mirror arranged to receive the reflection of said light flashes from said first mirror, a shutter interposed between sa'id mirrors for transmitting only a number of said flashes proportional to the sine of the angle which the longitudinal axis of said vehicle makes with the horizontal, said shutter being driven by the drive shaft of said vehic1e, a photocell arranged to receive reflected flashes of light from said second mirror, and means for indicating the responses of said photocell to said flashes of light 6. An apparatus according to claim 5 in which the second mirror is part of an ellipse having as its focal points the i'lrst mentioned mirror and the photocell.

7. An apparatus according to claim 5 in which means are provided for' damping the movement of the shaft carrying the pendulum.

8. An apparatus according to claim 5 in which electrical means are provided for exerting a forceon said shaft in opposition to a force exerted thereon'by acceleration or deceleration of the vehicle.

9. In a method for determining variations in elevation of terrain traversed by a vehicle, the

of said vehicle, an indicator, means for transmitting said signal to ksaid indicator, means interposed betweenthe point of creation of said signal and the indicator for fixing the number `of signals reaching the indicator ata value dependent upon the angle which the longitudinal axis of the vehicle makes with the horizontal.

EUGENE M. MCNA'I'I'.

t 4REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,203,738 Hines July 23, 1940 2,362,616 cloud Ney. 14, 1944;

FoRnIGN PATENTS I Number (lountry g 'Date 530,764 Germany ...n-... Aug. 1, 1931/ repetl- 

